Variable length records - wrong length READ

Originally, Enterprise COBOL V5.1 changed the behavior for wrong length READ compared to previous COBOL compilers; but for Enterprise COBOL V5.1 with current service applied, V5.2, and later versions, that behavior can be changed via a new compiler option, VLR(COMPAT|STANDARD) that was introduced to control whether you get the original standard-conforming behavior of COBOL V5.1 without service applied, or the behavior that is compatible with earlier COBOL compilers. It eases your migration from earlier versions to Enterprise COBOL V5 and V6, if your programs have READ statements that result in a record length conflict.

The 85 COBOL standard specifies the following rules as part of the processing of READ statements: If the number of character positions in the record that is read is less than the minimum size specified by the record description entries for the file, the portion of the record area which is to the right of the last valid character read is undefined. If the number of character positions in the record that is read is greater than the maximum size specified by the record description entries for file-name-1, the record is truncated on the right to the maximum size. In either of these cases, the READ statement is successful and an I-O status value of 04 is set indicating that a record length conflict has occurred.

This logic was correctly implemented in VS COBOL II, COBOL/370, COBOL for MVS & VM (except those compilers with the following APAR fixes installed), and Enterprise COBOL V5.1 without service applied, you would get the status value of 04 when READ statements encountered a record length conflict. However, if your programs are compiled with one of the following compilers, you get the status value of 00, which is the nonstandard result for READ statements.

VS COBOL II V1.3 with PTFs for APAR PN34704 installed
VS COBOL II V1.4 with PTFs for APAR PN38730 installed
COBOL/370 V1.1 or V1.2 with PTFs for APAR PN36445 installed
COBOL for OS/390® & VM, V2
Enterprise COBOL V3 or V4

The inconsistent behavior could have inhibited the migration to Enterprise COBOL V5 and V6. Thus, in Enterprise COBOL V5.1 with current service applied, V5.2, and later versions, you can choose to have the compatible and nonstandard behavior available with the VLR(COMPAT) compiler option.

If you specify VLR(COMPAT), you get File Status 00 when READ statements encounter a record length conflict or wrong length READ.

If your program performs a wrong length READ and your code checks for File Status=0 after reading variable-length record files, your code will take the "zero" path, just as it did in Enterprise COBOL V4 and earlier versions.

Note: This setting can hide I/O problems that can arise with the wrong length READ situation. Use the VLR(COMPAT) option with caution, and check for correct READ statements.
If you specify VLR(STANDARD), you get File Status 04 when READ statements encounter a record length conflict or wrong length READ. Using this setting, you can check for FS=04 and then add code to avoid accessing undefined data in a record and also avoid getting protection exceptions for attempting to reference a part of the record that was truncated.

If your program performs a wrong length READ and your code checks for File Status=0 after reading variable-length record files, your code will take the "Not zero" path. You can change your code to test for FS=0, while FS=4 and other values will all be a failed READ. For FS=4, you can add code to avoid the bad data in variables or protection exceptions.

Using VLR(STANDARD) can result in more reliable code and fewer I/O problems because the file status will tell you when a wrong length READ might occur. A new compiler message, MSGIGYP3178, can also help you avoid I/O problems by telling you if a program has a possibility of a wrong length READ. This message can be used to assist with migration from VLR(COMPAT) to VLR(STANDARD) by indicating the possible "wrong length READ" that you can solve by correcting the File Definition (FD). You can also raise the severity of the message so that the program must be corrected in order to run. To do this, use the MSGEXIT suboption of the EXIT compiler option to change the severity of message MSGIGYP3178 from I (RC=0) to S (RC=12), E (RC=8), or W (RC=4). If you are not interested in seeing this message, you can suppress the message completely.